In order to graph an equation of the line, you only need to know two point. This can be achieved by taking the x- and y-intercepts.
x-intercept:let y = 0
0 = x - 1
x = 1 (plot 1 on the positive x line)
y-intercept: let x=0
y = 0 - 1 = -1 (plot -1 on the negative y line)
Connect this two points and you obtain a line.